Electronically controlled electric motor provided for use in an environment containing solvents

ABSTRACT

An electronically controlled electric motor has, as position sensors ( 6 ), coils ( 5 ) which are arranged in a stator ( 2 ) and opposite permanent magnets ( 4 ) of a rotor ( 3 ). The coils ( 5 ) are produced integrally with connecting leads ( 7 ). This allows the electric motor to be used in an environment with solvents. Furthermore, the electric motor is of a particularly inexpensive design.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an electronically controlled electric motorintended for use in an environment with solvents, with at least onerotor bearing permanent magnets and a stator having coils, in whichmotor position sensors for ascertaining a commutating-time are arrangedin the stator.

2. Description of the Related Art

Such electric motors are often referred to as electronically commutatedDC motors and are used, for example, in fuel tanks for driving a fuelpump. If the coils are arranged in the stator, the electric motor doesnot require any carbon brushes for the transmission of electricalenergy. The electric motor is consequently distinguished as aninexpensive drive with a long service life in the lower and medium powerranges. Hall sensors are generally used as position sensors. The Hallsensors have semiconductor chips with terminal contacts. Thesemiconductor chips and the terminal contacts are usually sheathed inplastic. The disadvantage of the known position sensors is that thesemiconductor chips are of a very complex construction due to theirsheathing. Furthermore, the semiconductor chips, soldering points of theterminal contacts are not solvent-resistant in the long term. Plasticsheathings also cannot offer adequate protection against the diffusionof solvents, so that, in spite of sheathing, the semiconductor chips areattacked by the solvents. These occurrences of damage to thesemiconductor chips mean that the position of the rotor can no longer bereliably sensed by the position sensor.

SUMMARY OF THE INVENTION

The invention is based on the problem of designing an electric motor ofthe type stated at the beginning in such a way that it can be producedas inexpensively as possible and has a very high resistance to solvents.

This problem is solved according to the invention by the positionsensors having an electrical conductor which is induced by a movingmagnetic field to generate a signal and by the electrical conductorbeing produced integrally with connecting leads.

This design obviates the need for the position sensor of the electricmotor according to the invention to have any sheathing, since anelectrical conductor, such as a copper wire for example, is not attackedby solvents. As a result, particularly inexpensive position sensors canbe used in the electric motor according to the invention. The integralproduction of the electrical conductor with the connecting leads alsoallows the position sensor to be fitted very easily and not to requireany solvent-resistant soldering points. The electric motor according tothe invention can consequently be produced particularly inexpensivelyand has a very high resistance to the solvents. A further advantage ofthis design is that the position sensor can be arranged very close tothe magnet of the rotor, so that the position of the rotor can bedetermined particularly exactly.

The connecting leads of the position sensor could, for example, bescrew-connected to continuing leads, to avoid soldering points which arenot solvent-resistant. However, the fitting of the electric motoraccording to the invention is made even easier if the connecting leadsof the position sensor are led to a solvent-free space. In the case ofthe electric motor intended for driving the fuel pump arranged in thefuel tank of a motor vehicle, the connecting leads can consequently beled to outside the fuel tank.

According to another advantageous development of the invention, theposition of the rotor can be determined particularly exactly if theelectrical conductor is designed as a coil. For this purpose, the coilmay be arranged between the phase windings of the stator.

At particularly low rotational speeds of the rotor, the position of therotor can be easily determined according to another advantageousdevelopment of the invention if the electrical conductor is designed asa pulse wire arranged transversely with respect to the movement of themagnet poles of the rotor.

For reasons of space, it is often not possible to arrange the positionsensor within the coils of the stator. According to another advantageousdevelopment of the invention, the position sensor can be arranged at aposition remote from the permanent magnets of the rotor if the rotor hasposition magnets arranged away from its, permanent magnets and oppositethe position sensor. This also makes it possible to avoid a.falsification of the signals of the position sensor due to electriccurrents flowing in the coils of the stator. Furthermore, it is possibleto arrange in the electric motor according to the invention moreposition magnets than the rotor has permanent magnets. This allows theposition of the rotor to be determined particularly exactly.

In a further refinement, a disk which is subdivided into a plurality ofregions, the regions being differently magnetized, is arranged insteadof the position magnets.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention allows numerous embodiments. To illustrate their basicprinciple further, four of these are described below and represented inthe drawing, in which:

FIG. 1 shows a schematic representation of an electric motor accordingto the invention,

FIGS. 2 to 4 show further embodiments of the electric motor according tothe invention in schematic representations.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 3 schematically shows an electric motor with a housing 1 and acylindrical rotor 3 arranged on a rotatably mounted shaft 2. The rotor 3has a plurality of coils 5 opposite permanent magnets 4 of the rotor 3.The coils 5 are fastened in the housing 1. Position sensors 6 forsensing the position of the rotor 3 are arranged between the coils 5. Onthe basis of the signals of the position sensors 6, electric current fedto the coils 5 is controlled. The electric motor is often referred to asan electronically commutated DC motor. The position sensors 6 have ineach case electrical conductors 8 produced integrally with connectingleads 7 led to outside the housing 1. On the outer side of the housing1, the connecting leads 7 are connected to terminal contacts 9. At theseterminal contacts 9, control electronics (not represented) of theelectric motor can be connected. The electrical conductors 8 are woundto form a coil. When there is a rotation of the rotor 3, the permanentmagnets 4 generate induction currents within the electrical conductors 8wound to form the coil. The electrical conductors 9 are produced, forexample, from copper wire.

FIG. 2 schematically shows a further embodiment of the electric motor,in which the position sensors 6 have electrical conductors 10 designedas pulse wires. The electrical conductors 10 are arranged parallel tothe lateral surface of the rotor 3 and are produced integrally withconnecting leads 11. As in the case of the electric motor from FIG. 1,the position sensors 6 are arranged between the coils 5.

FIG. 3 schematically shows a further embodiment of the electric motor,in which a disk 13 having position magnets 12 is fastened on the shaft 2away from the permanent magnets 4 of the rotor 3. The position sensors 6are opposite the disk 13 with the position magnets 12 and areconsequently located in a position remote from the coils 5. The positionsensors 6 have electrical conductors 14 wound to form a coil.

FIG. 4 schematically shows a further embodiment of the electric motor,in which the position sensors 6 of the disk 13 have electricalconductors 15 which are opposite with the position magnets 12 and aredesigned pulse wires.

In each of the depicted embodiments, the motor operates in the presenceof a solvent 16 while the connecting leads 9 are led to a solvent-freespace.

What is claimed is:
 1. An electronically controlled electric motorcomprising: a shaft; at least one rotor having permanent magnets thereonfor rotation about the shaft; a stator housing having coils; and motorposition sensors arranged in the stator housing, wherein at least oneposition sensor comprises a solvent resistant electrical conductorproduced integrally with connecting leads; wherein a current is inducedin the electrical conductor by a moving magnetic field; and wherein therotor and position sensors operate in the presence of one or moresolvents and the connecting leads of the positions sensors arm led to aspace outside the presence of solvents.
 2. The electric motor as claimedin claim 1, wherein the electrical conductor is a coil.
 3. The electricmotor as claimed in claim 1, wherein the electrical conductor is a wirearranged parallel to the shaft.
 4. The electric motor as claimed inclaim 1, further comprising position magnets comprising a second set ofpermanent magnets positioned on a disk, wherein the disk and positionsensors are vertically displaced from the rotor and the disk is arrangedfor rotation about the shaft opposite the position sensors.
 5. Theelectric motor as claimed in claim 1, wherein the moving magnetic fieldwhich induces the current in the electrical conductor is generated bythe rotation of the permanent magnets on the rotor.
 6. The electricalmotor as claimed in claim 2, wherein the coil is coiled copper wire. 7.An electric motor for use in an environment containing solventscomprising: a stationary stator housing; a shaft through the statorhousing; a rotor positioned inside the stator housing for rotation aboutthe shaft, wherein the rotor contains one or more permanent magnetsthereon; one or more electrical coils fixed in the stator housing; oneor more position sensors fixed in the stator housing, wherein theposition sensors comprise solvent resistant electrical conductorsintegral with connecting leads, and wherein current is induced in theelectrical conductors by a moving magnetic field; and wherein the rotorand position sensors operate in the presence of one or more solvents andthe connecting leads of the positions sensors are led to a space outsidethe presence of solvents.
 8. The electrical motor as claimed in claim 7,wherein the electrical conductors are coils.
 9. The electrical motor asclaimed in claim 8, wherein the coils are coiled copper wires.
 10. Theelectrical motor as claimed in claim 7, wherein the electricalconductors are pulse wires arranged parallel to the shaft.
 11. Theelectrical motor as claimed in claim 7, further comprising a disk havingpermanent magnets thereon arranged for rotation about the shaft.
 12. Theelectrical motor as claimed in claim 11, wherein the moving magneticfield which induces the current in the electrical conductor is generatedby the rotation of the permanent magnets on the disk.
 13. The electricalmotor as claimed in claim 7, wherein the moving magnetic field whichinduces the current in the electrical conductor is generated by therotation of the permanent magnets on the rotor.
 14. The electrical motoras claimed in claim 10, wherein the pulse wires copper wires.